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Peptide Evidence Registry

Growth hormone axis · Metabolic & endocrine

IGF-1 LR3

A modified long-acting IGF-1 analogue sold for bodybuilding, and not the same thing as approved IGF-1 medicine.

L1Theory onlyNot approved for this useUnclearPeptide analogue
How settled this rating is:
very-low confidence in the current evidence rating
Routes studied:
Not established · Subcutaneous injection, Intramuscular (marketed but never approved)
Also known as:
long R3 IGF-1, IGF-1 Long R3
Last reviewed:
2026-09-21
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Evidence passport

IGF-1 LR3

A one-screen evidence identity for this compound. These fields describe research maturity, confidence and legal status. They are not a safety guarantee, efficacy percentage or recommendation.

Reviewed 2026-09-21
Evidence level
L1Theory only
Confidence
Very low confidence in rating
Regulatory status
Not approved for this use
Development status
Unclear

Evidence strength

Human efficacy evidence5 of 100 evidence strength

Higher = more and better-quality human evidence. It does not mean the effect is bigger or that the compound works for you.

Human safety evidence8 of 100 evidence strength

Higher = more mature, better-documented human safety data. It does not mean the compound is safer than one with a lower number.

The 0-100 values rate the strength and maturity of evidence, not how effective or safe the compound is.

Evidence base
Mostly animal and laboratory research
Furthest established stage
Not established
Human research maturity
No adequate human trial evidence for the LR3 analogue itself
Source curation
Sources fully curated

Routes recorded

SC injection· unapprovedIM· unapproved

Most of this evidence comes from animals and cells

The supporting research for IGF-1 LR3 is predominantly preclinical (Level 1–2). That is a legitimate starting point for science and a poor basis for personal decisions. Human results are not simply a scaled-up version of mouse results.

Overview

Human efficacy evidence strength5 of 100 evidence strength

Higher = more and better-quality human evidence. It does not mean the effect is bigger or that the compound works for you.

Preclinical (animal / lab) evidence strength40 of 100 evidence strength

Higher = more animal, tissue or cell research. Preclinical results are a starting point, not proof of a human benefit.

Human safety evidence strength8 of 100 evidence strength

Higher = more mature, better-documented human safety data. It does not mean the compound is safer than one with a lower number.

How to read these scores

Every number here rates the evidence, not the compound. They are editorial 0-100 strength ratings, not percentages, and not a rating out of five stars.

  • Human efficacy evidence strength — Higher = more and better-quality human evidence. It does not mean the effect is bigger or that the compound works for you.
  • Preclinical evidence strength — Higher = more animal, tissue or cell research. Preclinical results are a starting point, not proof of a human benefit.
  • Human safety evidence strength — Higher = more mature, better-documented human safety data. It does not mean the compound is safer than one with a lower number. A score of 80 does not mean “80% safe”.
  • Evidence level (L0-L5) — the strongest type of study behind the compound, from anecdote (L0) to large replicated human trials (L5). It is a description of the study evidence, not a quality, safety or recommendation rating.
  • Confidence — how likely we think it is that this rating changes as new research lands. Low confidence means the picture is unsettled, not that the compound is bad.

None of these ratings is medical advice, a safety guarantee, or a recommendation to use anything. How we grade evidence.

How far human research has progressed: No adequate human trial evidence for the LR3 analogue itself

Routes & formulations

Marketed / research routes — never approved

SC injection· unapprovedIM· unapproved

Marketed for injection. Approved IGF-1 therapy exists as a supervised medicine for defined rare conditions; that approval provides no support for research-market LR3 products.

Route availability is not evidence of efficacy, and evidence from one route does not transfer to another. The Registry never provides dosing or sourcing information.

Peptide lifecycle

  1. Discovery

  2. Preclinical

  3. Phase I

  4. Phase II

  5. Phase III

  6. Approved

UnclearFurthest stage not established in our curated record

There is no pharmaceutical development programme for IGF-1 LR3 in our record. It exists primarily as a laboratory reagent and research-market product.

What it is

A modified version of IGF-1 with an extended N-terminal sequence and an amino-acid substitution that reduce binding to IGF binding proteins, giving a longer-acting molecule originally made for cell-culture research.

What people claim

  • Muscle growth and hyperplasia
  • Nutrient partitioning and fat loss
  • Enhanced recovery between training sessions

What the evidence actually says

Primary human evidence for LR3 specifically is thin to the point of absence — we say that plainly rather than borrowing credibility from approved IGF-1 medicine. What exists is IGF-1 receptor biology, cell-culture data, and a large volume of community reporting. The relevant risks here are twofold: an unresolved growth-signalling question and a completely unregulated supply chain.

Related evidence

Useful next reads based on this compound — not recommendations.

Human evidence

  • No adequate controlled human trial of IGF-1 LR3 for muscle, performance or body-composition outcomes was identified in our curated record.
  • A 2026 peer-reviewed review documents IGF-1 LR3 among substances self-administered outside medical supervision — a use pattern, not an efficacy finding.
  • Approved recombinant IGF-1 evidence applies to a different product and different patient populations.
  • The molecule is documented, and that is a separate matter from any product. Native human IGF-1 is a 70-amino-acid polypeptide hormone; pharmaceutical recombinant human IGF-1 exists as the approved medicine mecasermin; and Long R3 IGF-1, R3 IGF-1 and DES(1-3) IGF-1 are real, published analogues, with recombinant expression and measurable IGF-1 receptor activity reported for LR3 in the laboratory. None of that is evidence about what is inside an unregulated vial, and none of these modified analogues is an approved human medicine.
  • Establishing that a supplied product is what it claims requires analytical evidence on that material — mass spectrometry, sequencing or intact-mass confirmation can speak to identity and purity. Correct folding and disulfide pairing, labelled quantity and biological activity are further separate questions, and an HPLC purity figure on its own does not demonstrate a correctly folded, bioactive protein.

Preclinical evidence

  • Cell-culture and animal work on IGF-1 receptor signalling, protein synthesis and satellite-cell proliferation.

Animal and cell findings are Level 1–2 evidence.

Mechanism and pathways

  • IGF-1 receptor agonism drives anabolic signalling pathways in muscle and other tissues.
  • Reduced binding-protein interaction increases free activity — which also removes a natural regulatory brake.

Molecule legitimacy is not product authenticity

Molecule legitimacy is not product authenticity. A molecule can be scientifically real, documented in peer-reviewed work and still tell you nothing about what is inside a vial someone sold you. These are four separate questions, and evidence for one is not evidence for the next.

  1. Is the molecule scientifically real and documented? — Evidence can establish this

    Often yes, and published work can establish it — sequence, recombinant production and measurable receptor activity in the laboratory.

  2. Is it an approved medicine? — A separate question

    A separate question with a separate answer. Being real and being licensed for human use are unrelated.

  3. Does a vial bought online contain the stated molecule? — Cannot be assumed

    Cannot be inferred from the label, the name, the price or a certificate supplied by the seller. Only independent analysis of that material speaks to it.

  4. Is it correctly folded, pure, correctly quantified and biologically active? — Cannot be assumed

    Four more separate questions. Mass spectrometry, sequencing or intact-mass work can address identity and purity; folding and biological activity need functional evidence. A purity chromatogram alone does not show a correctly folded, active product.

Safety and unknowns

  • Hypoglycaemia is a recognised hazard of IGF-1 pathway activity and is described in approved IGF-1 labelling.
  • No human safety dataset exists for LR3 products, and content and purity of unregulated material are unverifiable.

Cancer relevance

This section covers questions raised by how the compound works in the body, plus anything regulators and trial teams keep an eye on. It is not a statement that this compound causes cancer — for most compounds here, no human data exist in either direction.

Theoretical / mechanistic concern only

Sustained IGF-1 receptor signalling is one of the better-grounded theoretical cancer concerns in this field, given its role in cell proliferation. That is a mechanistic concern, not a demonstrated human risk for this product — and the absence of studies is not reassurance.

Regulatory status

Regulatory decisions apply to specific jurisdictions, products, formulations and indications. An approval elsewhere is not automatically an approval in your country.

Check the regulatory note and linked primary sources for jurisdiction-specific details.

Not an approved medicine in any region. It must not be confused with approved recombinant human IGF-1 (mecasermin), which is licensed for specific rare growth disorders under medical supervision and is a different product with a different evidence base. IGF-1 LR3 is prohibited in sport.

Evidence grade

L1Theory onlyVery low confidence in rating

Mechanistic rationale or early development without qualifying compound-specific outcome evidence. A registered trial is not a result.

What would change our rating?

  • Controlled human data on the LR3 analogue itself.
  • Any regulated safety or pharmacokinetic dataset.

References and sources

Source transparency

A provenance snapshot of this profile. Counts show what kinds of sources are cited, not how much scientific weight each source deserves.

Sources fully curated
Last editorial review
2026-09-21
Recently reviewed · 30 days ago
Linked curated sources
3
Sources still pending
0
External specialist reviews
0
None recorded for this profile
Peer-reviewed: 3

Review provenance

Registry editorial review: Colin Jackson-White, creator and editor, who is not a doctor or clinician. External specialist review is credited only when a named reviewer has completed a review of this exact profile.

Literature-discovery and AI tools may help locate or challenge candidate evidence, but they are not counted as evidence sources here. Registry judgements are tied to the underlying papers, trial records, regulator documents and official study records.

Source hierarchy: regulatory documents and trial registries first, peer-reviewed work next, sponsor material flagged as non-independent. We never use supplier or clinic marketing as evidence, and where a verified source has not yet been curated we say so rather than inventing one.

Evidence change history

These entries record changes to our assessment of the published evidence — not changes to the compound itself.

  1. The IGF-1 LR3 profile now states plainly that native IGF-1 is a legitimate 70-amino-acid polypeptide hormone, that pharmaceutical recombinant IGF-1 exists as mecasermin, and that LR3, R3 and DES(1-3) IGF-1 are documented analogues with published recombinant expression and measurable receptor activity — alongside a reusable four-question ladder separating those facts from what is inside an unregulated vial.

    Change 1 of 1
    L1Theory only
    No rating change. The molecule literature is laboratory work and none of these analogues is an approved medicine. Identity and purity of a supplied product need analytical evidence on that material; folding, labelled quantity and biological activity are further separate questions, and a purity figure alone does not demonstrate a correctly folded, active protein. Reviewed 21 September 2026.

Related claims we’ve checked — in full

Claim verdict

Molecule legitimacy vs product authenticity

MisleadingL1Theory only

“IGF-1 LR3 is a real, documented molecule, so a vial sold online is the real thing.”

This verdict applies to the exact claim above. It is not a verdict on the compound overall, a safety guarantee, or a recommendation to use it.

Registry verdict

Misleading — the molecule being real says nothing about what is in the vial.

Why this verdict

  • Two separate questions get collapsed into one. Native human IGF-1 is a legitimate 70-amino-acid polypeptide hormone, pharmaceutical recombinant IGF-1 exists as the approved medicine mecasermin, and Long R3 IGF-1, R3 IGF-1 and DES(1-3) IGF-1 are documented analogues with published recombinant production and measurable IGF-1 receptor activity in the laboratory.
  • None of those modified analogues is an approved human medicine, and none of that literature was produced using grey-market material.
  • Whether a supplied vial contains the stated molecule cannot be read off the label, the name or a seller-supplied certificate. It requires analysis of that material.
  • Identity and purity can be addressed by mass spectrometry, sequencing or intact-mass confirmation. Correct folding and disulfide pairing, labelled quantity and biological activity are further separate questions — an HPLC purity figure alone does not show a correctly folded, active protein.